Shear Assisted Processing and Extrusion (ShAPE) of Al-Ce and Al 7075 Aluminum Alloys

Shear Assisted Processing and Extrusion (ShAPE) is an emerging technology for the manufacture of extruded metal components with improved performance and lower embodied energy. The application of ShAPE to Al-Ce and Al 7075 alloys will be discussed as illustrative examples. Al-Ce castings (Al-8Ce-4Mg) are known for their retention of tensile properties at elevated temperature which is attractive for aerospace applications. However, the brittle intermetallic phases that enable high temperature stability also make the alloy difficult to extrude. Al-8Ce-4Mg castings were easily extruded by ShAPE and achieved a highly refined microstructure with mechanical properties that include a doubling of yield strength and near tripling of toughness compared to conventionally extruded Al-8Ce-4Mg tested under identical conditions. Microstructural analysis shows increasing comminution of second phase particles as process temperature decreases, which is attributed to higher load transfer from the Al matrix into the particles. The potential for ShAPE to improve, or even eliminate, process steps common to conventional extrusion will be illustrated for Al 7075. Here Al 7075 castings were extruded at up to 12 meters/min, far exceeding the 1-2 meter/min limit for conventional extrusion while still meeting property specifications. Additionally, Al 7075 castings were extruded in the unhomogenized condition, eliminating the requirement for a thermal homogenization treatment at 465 °C for 18-24 hours. Microstructural analysis shows that extensive refinement and dispersion of second phases occurs during ShAPE extrusion.